liner material removal to reduce pumping losses

[Swiss Toni]

1 hour ago, baldrick said:

 

Doh! 

 

cheers for clearing that up, in all the years ive had these ive never even noticed before, worra nugget eh ? 

Me too! That’s the piece I told you was broken. 

[gsxr1385]

On 11/15/2022 at 12:27 PM, dupersunc said:

The volume isn't changed but you do have displacement and flow. As it's actually an oil air mist, it's quite dense, so takes even more energy to move it the air volume around the crankcase. The energy required is squared as the speed of the piston doubles, so at 10,000rpm you are using a lot of energy to move the mist around the crank case, that energy is turned into heat, which causes more power loss.  Shorten the path via windows in the liners, or by smoothing the edges of the webs in the crank to improve flow for the displaced air/oil mist reduces the energy it takes to do so.

all well proven physics. It's why race engines run dry sumps with a depression in the crank case and have huge amounts of detail work on the inside of the cases.  Ducati even run vacuum pumps on wet sump engines.

I guess we are just going to have to disagree. While I will agree that high velocity moving parts in a crankcase that can move more easily in the high temperature oil/air mixture (say by smoothing edges) will reduce horsepower requirements, I do not agree that those little notches in the liners is reducing energy required to move displaced oil/air mixture to any measurable degree regardless of speed / RPM.  Fluids and gases will take the path of least resistance. How can a claim be made that any volume is passing through those notches, especially considering the available volume in the crankcase to displace say 335 cc (in a big bore engine) is so much more and provides less resistance to flow than passing that volume through those notches. An analogy would be a suspension system damper - which is the path of least resistance, force liquids through an orifice or into a larger volume reservoir?

That is engineering judgement and physics. And reinforced by not seeing that feature in all manner of racing engine internals, and industrial pumps, reciprocating compressors, etc.

I suspect it is just one of those experiments someone tried on a racer to try and gain a small advantage, and then became one of those "old racers tales" that get circulated through the years. However, if someone can produce data and test protocols from controlled testing that conclusively proves a horsepower savings from that feature, I'm willing to look at it - (someone saying that Suzuki says so, just isn't convincing).

[bluedog59]

You have an inlet tract 100mm long, 25mm I/d . Do you make it straight or zigzag shape ?

[imago]

1 hour ago, gsxr1385 said:

I guess we are just going to have to disagree. While I will agree that high velocity moving parts in a crankcase that can move more easily in the high temperature oil/air mixture (say by smoothing edges) will reduce horsepower requirements, I do not agree that those little notches in the liners is reducing energy required to move displaced oil/air mixture to any measurable degree regardless of speed / RPM.  Fluids and gases will take the path of least resistance. How can a claim be made that any volume is passing through those notches, especially considering the available volume in the crankcase to displace say 335 cc (in a big bore engine) is so much more and provides less resistance to flow than passing that volume through those notches. An analogy would be a suspension system damper - which is the path of least resistance, force liquids through an orifice or into a larger volume reservoir?

That is engineering judgement and physics. And reinforced by not seeing that feature in all manner of racing engine internals, and industrial pumps, reciprocating compressors, etc.

I suspect it is just one of those experiments someone tried on a racer to try and gain a small advantage, and then became one of those "old racers tales" that get circulated through the years. However, if someone can produce data and test protocols from controlled testing that conclusively proves a horsepower savings from that feature, I'm willing to look at it - (someone saying that Suzuki says so, just isn't convincing).

It really isn't an "engineering judgement and physics" at all. What you're trying to argue against is the exact principle on which two stroke engines operate, movement and flow of gasses under compression.

Your damper analogy is way off. Firstly because fluid and gas dynamics are completely different (that is physics) and you're also comparing an accelerating compressed gas (can't compress a liquid, again physics) moving from a higher pressure to a reduced pressure (depression caused by piston moving up) with a fluid being forced to move through a restriction in order to slow it.

You are of course entitled to your opinion, just not to rewrite the laws of physics.

[gsxr1385]

2 hours ago, imago said:

It really isn't an "engineering judgement and physics" at all. What you're trying to argue against is the exact principle on which two stroke engines operate, movement and flow of gasses under compression.

Your damper analogy is way off. Firstly because fluid and gas dynamics are completely different (that is physics) and you're also comparing an accelerating compressed gas (can't compress a liquid, again physics) moving from a higher pressure to a reduced pressure (depression caused by piston moving up) with a fluid being forced to move through a restriction in order to slow it.

You are of course entitled to your opinion, just not to rewrite the laws of physics.

I do understand engineering and physics, unlike you that only understands how to google a subject and then spews out the results in a jargon laced diatribe that is not even applicable to the issue being discussed.

It is not my job to educate you, but I will make a few points. First comparing the situation under discussion to the operation of a two-stroke engine (the pressurized flow of fuel intake and exhaust through the cylinder ports in a closed combustion chamber) is baffling because it doesn’t apply at all. I’ll leave it at that. 

Even more baffling is you bringing up the subject of compressibility of gases and liquids and their resultant fluid flow characteristics. We aren’t comparing gas vs liquid flow; we are comparing the flow of an oil/air mixture via two different paths. Bizzare. The principle here is the path of least resistance - pushing a gas, gas/liquid mixture, or a liquid through an orifice will result in a pressure drop and impede flow. And the higher the velocity of that mixture, the greater the resistance to flow (velocities greatly increase through your notch pathway vs the reservoir path). You do not understand fluid dynamics, Bernoulli's principles, etc. so stop pretending you do.

Let me see if I can put this in more easily visualized terms - you are arguing that it is easier to push a 335 cc oil/air mixture (of a downward moving big bore piston) through an orifice (or two series notches of about 6-10 cc) into a 335 cc cavity, than it is to dump it into a large reservoir (say about 5000-6000cc) which is at a lower pressure (vented to atmospheric pressure or even lower from which that volume can be displaced out of the engine). And you are similarly saying that the simultaneous upward piston movements will draw through those two notches before it will draw from that large reservoir that is at a lower pressure. That reservoir also undulates with 2 more +/- piston movements that all 4 equate to zero volume changes at any crankshaft position. If fact, I'd be surprised if there is any flow through those notches' vs the crankcase path. So, who is rewriting the laws of physics?? If you understood those laws, you would recognize it is you. But you don’t.

When you get a master’s degree in mechanical engineering, a minor in physics, 40 years of experience in applying your efforts to effect solutions that actually work, then we can have an intelligent discussion. Until then, or if you can provide data and testing protocols from a controlled test that prove your point, we have nothing further to discuss.

[Captain Chaos]

[imago]

8 hours ago, gsxr1385 said:

When you get a master’s degree in mechanical engineering, a minor in physics, 40 years of experience in applying your efforts to effect solutions that actually work, then we can have an intelligent discussion. 

If that's true then you really should ask for your money back, because I'd expect an engineer to have a better grasp of basic physics. 

The only thing I'll add is that "we" weren't talking about fluids until you decided to use a shock absorber for comparison. Perfectly illustrating how little you actually know of the subject. 

[dupersunc]

9 hours ago, gsxr1385 said:

I do understand engineering and physics, unlike you that only understands how to google a subject and then spews out the results in a jargon laced diatribe that is not even applicable to the issue being discussed.

It is not my job to educate you, but I will make a few points. First comparing the situation under discussion to the operation of a two-stroke engine (the pressurized flow of fuel intake and exhaust through the cylinder ports in a closed combustion chamber) is baffling because it doesn’t apply at all. I’ll leave it at that. 

Even more baffling is you bringing up the subject of compressibility of gases and liquids and their resultant fluid flow characteristics. We aren’t comparing gas vs liquid flow; we are comparing the flow of an oil/air mixture via two different paths. Bizzare. The principle here is the path of least resistance - pushing a gas, gas/liquid mixture, or a liquid through an orifice will result in a pressure drop and impede flow. And the higher the velocity of that mixture, the greater the resistance to flow (velocities greatly increase through your notch pathway vs the reservoir path). You do not understand fluid dynamics, Bernoulli's principles, etc. so stop pretending you do.

Let me see if I can put this in more easily visualized terms - you are arguing that it is easier to push a 335 cc oil/air mixture (of a downward moving big bore piston) through an orifice (or two series notches of about 6-10 cc) into a 335 cc cavity, than it is to dump it into a large reservoir (say about 5000-6000cc) which is at a lower pressure (vented to atmospheric pressure or even lower from which that volume can be displaced out of the engine). And you are similarly saying that the simultaneous upward piston movements will draw through those two notches before it will draw from that large reservoir that is at a lower pressure. That reservoir also undulates with 2 more +/- piston movements that all 4 equate to zero volume changes at any crankshaft position. If fact, I'd be surprised if there is any flow through those notches' vs the crankcase path. So, who is rewriting the laws of physics?? If you understood those laws, you would recognize it is you. But you don’t.

When you get a master’s degree in mechanical engineering, a minor in physics, 40 years of experience in applying your efforts to effect solutions that actually work, then we can have an intelligent discussion. Until then, or if you can provide data and testing protocols from a controlled test that prove your point, we have nothing further to discuss.

The notches in the bottom of the liner and other crank case work increase flow. 

The notches allow a path of less resistance. 

The notches are not creating an extra orifice, they are opening up, increasing the size of a path that is already there.

[imago]

In the workshop now, so I can use the computer instead of peering at the phone.

Everything that's happening takes place in fractions of a second. So it can only be viewed as a snapshot with a nod to what happens from that point.

At the bottom you have the oil, a liquid which can't be compressed (green band on the sketch), above that there is oil foam which is a mass of bubbles that is denser than the gasses but less dense than the liquid (green circles), above that there is a layer of dense gas which has a high percentage of oil particles in the form of mist (blue circles) above that is a thin layer of compressed gas, and above that there are four (two drawn) columns of gas which are at a constantly fluctuating pressure due to the pistons moving up and down the bores (red and black respectively). The only part of that which can easily be changed are the behaviour of the four columns.

It should be said at this point that there is constant mixing and blending between the layers. This can only happen if you have energy to do so, that comes from the heat present. Vibration also plays a part, but leave that aside as it's complicated enough for now.

When the left hand piston is travelling down the pressure above it (which you want) is pushing against the pressure below. The further down that piston travels the greater the pressure it has to overcome. So if you cut a slot/port/hole/gap at the bottom of the liner the pressure below which is fighting against the pressure above is reduced as it has a path of lesser resistance. If you cut that slot between the left and right bores (orange arrow) the pressure which is now dropping in the right hand bore helps that process further because of the reduced pressure caused by the piston rising. So you have a small but significant reduction in the power needed to overcome the pressure below the left piston. You also have a smaller, but no less significant benefit, by reducing the 'suction' fighting against the rising piston on the right.

The principle and effect are the same as a weather system over the sea. Varying pressures and temperatures causing changes of state and winds.

 

So it's not trying to change the volume. It's allowing movement of the pressure build up beneath a piston, which reduces that pressure spike.

Edited November 17, 2022 by imago
typo/s

[imago]

3 hours ago, Captain Chaos said:

[bluedog59]

Firstly I would like to suggest that introducing personal attack and slander into a discussion is neither endearing to oneself or affirming of your opinion. In a similar vein, pontificating that you are in possession of a piece of paper does not ensure the validity of your argument in every situation. In simple terms, the fact that I have a big cock does not guarantee I am a good shag.

Secondly, Would anyone care to answer my previously asked question regarding a hypothetical inlet and it's shape ?

[imago]

16 minutes ago, bluedog59 said:

Firstly I would like to suggest that introducing personal attack and slander into a discussion is neither endearing to oneself or affirming of your opinion. In a similar vein, pontificating that you are in possession of a piece of paper does not ensure the validity of your argument in every situation. In simple terms, the fact that I have a big cock does not guarantee I am a good shag.

Secondly, Would anyone care to answer my previously asked question regarding a hypothetical inlet and it's shape ?

Sorry dad, but he started it! 

On the second point. Inlet tract shapes are a bit of a dark art and not something I'd claim to know enough about to be sure. But from what I remember you need to increase velocity, so I'd say straight-ish but tapering?

[bluedog59]

I'll take that as a +1 for "straight" rather than "zigzag".

NB. For clarity we will not concern ourselves with tapers, surface finish or suchlike at this point.

[Wagola]

3 hours ago, bluedog59 said:

 pontificating 

Love that word !! and I love pontificating! Although procrastinating is good too ?

Nice to see the art of discussion is alive and well. Not that I really understand any of it.

Just saying.

[bluedog59]

29 minutes ago, Wagola said:

 "procrastinating"

Ermm, can I come back to you in a minute about that ?

[gsxwill]

Enjoying the topic and the passion 

[coombehouse]

On a slight tangent, I have a gsxr1000 that was set up & dynoed by crescent Suzuki when they were racing them. They modified the pair system to draw air from the crankcase, something they did on all their race bikes back then. Whenever I remove the oil filler cap, there is a hiss as the vacuum escapes. No idea of its effectiveness but I've often considered connecting the breather on my katana to the exhaust to see if it makes any difference. 

[Gixer1460]

4 hours ago, coombehouse said:

On a slight tangent, I have a gsxr1000 that was set up & dynoed by crescent Suzuki when they were racing them. They modified the pair system to draw air from the crankcase, something they did on all their race bikes back then. Whenever I remove the oil filler cap, there is a hiss as the vacuum escapes. No idea of its effectiveness but I've often considered connecting the breather on my katana to the exhaust to see if it makes any difference. 

The use of electric vacuum pumps on ProStock bikes used to be popular on the 4 cylinder engines and the use of PCV valves in exhaust headers just before the megaphone was also a thing 'back in the day' - all to get less 'windage' in the crankcases.

[jonny1bump]

If I remember correctly the vac pumps gave 8 to 12 hp on the stockers.

Edited November 21, 2022 by jonny1bump

[TLRS]

Not sure this is entirely appropriate but anyone who’s interested in genius engine tuning might want to listen to Steve Dinan. There is a podcast where he tells about reducing friction. Besides the dry sump, lower pressure and reduced losses. He talks about reducing piston ring pressure as there is less blowby. Machining the circumference of the pistons to reduce friction. Increase rodlength. And putting jets in oil gallery to reduce oil requirements to what’s necessary for hot weather racing.

I forgot which rules he had to stick with, but it limited the usual suspects for power increases. Like compression, cams and valve sizes or something.

It’s all % here and there but managed a very substantial result in the end.

[Gixer1460]

5 hours ago, TLRS said:

 He talks about reducing piston ring pressure as there is less blowby.

Bit wary of this - Toyota have followed this route with millions of car engines in pursuit of improved economy (which it did) only to get thousands of warranty claims for major excessive oil consumption / top & bottom end failures due to low oil at really low mileages. As always 'there is no such thing as a free lunch' & if an OEM can get caught out ! !. 

Machining of the piston skirts is the basis of the 'slipper' style piston, they are ok for racing but the piston slap noise in a road engine is unacceptable IMO. There are loads of 'secrets' for reducing friction / rotating mass - like slimming down crank counterweights so x sectional area is less and so less windage then add back the weight at the tips using Tungsten slugs. Simple, effective but costly unless racing.

[coombehouse]

3 hours ago, Gixer1460 said:

Bit wary of this - Toyota have followed this route with millions of car engines in pursuit of improved economy (which it did) only to get thousands of warranty claims for major excessive oil consumption / top & bottom end failures due to low oil at really low mileages. As always 'there is no such thing as a free lunch' & if an OEM can get caught out ! !. 

Machining of the piston skirts is the basis of the 'slipper' style piston, they are ok for racing but the piston slap noise in a road engine is unacceptable IMO. There are loads of 'secrets' for reducing friction / rotating mass - like slimming down crank counterweights so x sectional area is less and so less windage then add back the weight at the tips using Tungsten slugs. Simple, effective but costly unless racing.

Gurls blouse did the low tension ring thing on 2008 blades too. Many drank oil, they modified the rings for 2009 onwards which fixed the problem. 

[TLRS]

16 hours ago, Gixer1460 said:

Bit wary of this - Toyota have followed this route with millions of car engines in pursuit of improved economy (which it did) only to get thousands of warranty claims for major excessive oil consumption / top & bottom end failures due to low oil at really low mileages. As always 'there is no such thing as a free lunch' & if an OEM can get caught out ! !. 

Machining of the piston skirts is the basis of the 'slipper' style piston, they are ok for racing but the piston slap noise in a road engine is unacceptable IMO. There are loads of 'secrets' for reducing friction / rotating mass - like slimming down crank counterweights so x sectional area is less and so less windage then add back the weight at the tips using Tungsten slugs. Simple, effective but costly unless racing.

Totally agree that a lot of it is expensive or too fragile for a decent street engine. But it’s fascinating stuff!

[Buzuki]

17 hours ago, coombehouse said:

Gurls blouse did the low tension ring thing on 2008 blades too. Many drank oil, they modified the rings for 2009 onwards which fixed the problem. 

Also not enough oil return holes number on the piston oil groove just behind the oil ring caused abnormal high oil consumption .